I'm glad I came here... I would've never considered that a valid solution. If I was in a gang and the leader was killed, I'd see it as a promotion for me... and I'd certainly not let a group of civies get away with putting a hit on my gang. They'd all die, for sure. On the other hand, community consensus is that wiping out a leader gets rid of the gang, who am I to argue? I see it wrong, apparently. 
So, we've added a possible solution. Anything else? Does it sound like a fun/interesting run? Too cookie cutter boring? I know it's generally bad to railroad the group into a specific action, but we've spent 2 months of gaming doing our best to avoid any combat. The whole point of this run is to force them into a few fights, to some degree or another. In my best case scenario, they would go through the compound(I'm thinking multiple buildings that share a common area with a fountain in the middle) quietly and wipe out everyone they find, a la Splinter Cell. Kill everyone, loot everyone, everyone is happy.
Have a think about what to do if it doesn't go smoothly. Chances are that the gang will become alert at some point in time. Someone will get a shot off, or scream or maybe someone just stumbles on their bodies.
If the gang has magic, then they have watch spirits which could also add complications.
Have a twist, at least one simple twist. Why are they anti-tech? Perhaps they have a spirit mentor? Or maybe a rival gang chooses to raid the complex at the same time? Or something else? Something simple that throws a spanner in the works. Heck, throw some domesticated hell hounds in the mix.
A lot of ideas will depend on how your group plays. This scenario appears to be a combonation of shooter/dungeon crawl style.
Think about how to keep the game tense and exciting. Think of challenges they they may need to deal with. Any traps, trip wires etc? A bridge joining to building across a wide open space, connected basement area, tight and narrow and filled with steam pipes, dripping water, barrackaded, mined, corridors, etc, etc.
Put some thought into giving the gangers some character. Not too much, likely chances are your runners will kill them pretty quick, but maybe one of the girls has a pink mohawk, one the trolls thinks his niel the barbarian, the shaman is a rat shaman and keeps a swarm of rats patrolling the complex. So that rat they just killed? His buddy went and warned his master.
Anyway, just a few thoughts.